In order to terminate a participants registration at the end of the current term you can use the Star Tracker. For details or custom settings please use the super user interface.
Click the 'Edit' icon on the participant to see the edit window.
Click on *3* in order to end the registration. This will set the participants 'end registration date' on the current registration.
After updating the view you will see the icon indicating that participant has end registration date set (registration terminated at end of term). Touch/hover icon to see exact date
Next time you open the participants edit window all three buttons are disabled. Alter this via the super user interface if reopening is needed.